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Bronzes and Brasses.                           8 5

portions vary somewhat, depending on the colour and strength


Parts Copper %         Parts Zinc p/0
Fine yellow brass has       ...    66*6        ...        33*3

The proportion of copper may vary from 66 to 70 per cent, or
even higher. A little lead is sometimes added. Brass is principally
used on account of its fine colour, and because it is easily tooled.

(10.) Muntz Metal is a brass having the proportion of 60
per cent, of copper and 40 per cent, of zinc. It is largely used
for bolts in marine work that are liable to rust, and especially for
pins that have to turn in their sockets, on account of its great
strength, as well as the faculty of being forged, which it possesses,

(n.) Phosphor Bronze is, like gun metal, a mixture of
copper and tin, but with the addition of a small measured quantity
of phosphorus. (See Appendix /,/. 748.)

Its strength is then so much increased as to be equal to that
of wrought iron, and it has consequently been extensively used,
within recent years, where strength is required, coupled with
intricate form, such as must be cast rather than forged; as for
example, toothed wheels subjected to shock. Gun metal is
deteriorated by subsequent meltings, while phosphor bronze may
be re-melted without injury.

It has considerable ductility, and may be formed into wire, and
used for spiral springs subjected to steam or water.

(12.) Manganese Bronze, introduced later, is really a
yellow brass, to which about 7 Ibs. of cupro- or ferro-manganese
have been added per cwt. of the metal. The strength is thereby
still more increased ; and it is used now for a variety of purposes
where strength and ductility are required combined, such as
hydraulic pipes, which may be then drawn considerably thinner
than copper ones; and it is advantageous in many other cases,
as may be understood from the fact that it way be both cast into
moulds and forged under the hammer. It can also be used to
rust, so as to keep nuts and bolts free that would otherwise
seize. (Set App. //., p. Sot.)

< (15,) White Metal, otherwise white brass, and in America
Babbitt's Metal, or * Babbit/ is an alloy used for lining bearings.
Tin is the principal metal used, and is mixed with copper and